This invention relates generally to testing methods for carpets and other floor coverings and, more particularly, to methods of obtaining meaningful comparative data regarding the performance and functional characteristics of such coverings.
The ultimate test of a floor covering's performance is how well it actually performs in service. Such empirical testing is usually impractical, however, in that carpets and other floor coverings can serve for years before serious design flaws or other inadequacies become apparent. Furthermore, conscientious and responsible floor covering manufacturers need to test their products thoroughly before placing them on the market. Allowing an inferior product to reach the marketplace can harm a manufacturers' reputation and reduce its market share. Accordingly, manufacturers cannot afford to use the marketplace itself as a testing or proving ground for their products. Floor covering manufacturers thus have a need for accurate, reliable and effective test procedures and methods in order to obtain meaningful performance data regarding their products.
Floor covering testing is also of importance from a consumer's point of view. Floor coverings not only represent a sizable monetary investment but can affect a consumer's health and well-being as well. Inappropriately selected floor coverings can contribute to falls, aggravate musculo-skeletal disorders and adversely affect indoor air quality. For the purchaser who ultimately has to live with whatever floor covering is purchased and installed, there is too much risk in buying an unproven product. Consumers, too, need access to accurate, reliable and meaningful test data regarding floor coverings.
Because of the impracticality of waiting to see how a particular floor covering performs in actual service, a variety of techniques have been proposed for predicting the performance of particular floor coverings. Typically, the general approach is to accelerate the apparent wear in a floor covering sample. This can be achieved, for example, by placing a floor covering sample in an actual high traffic area or by simulating pedestrian traffic using a machine. Although such approaches have been effective in substantially reducing the time needed to cause noticeable wear in a floor covering sample, neither approach has been totally satisfactory in providing reliable, reproducible and ultimately valuable test information.
A principal difficulty in using actual pedestrian traffic for testing purposes is the lack of uniformity and repeatability in the test conditions. For example, the actual number of footfalls landing on the sample typically is not known with total accuracy. Similarly, ambient conditions, such as temperature and humidity, can vary from day to day or from test site to test site. Finally, the soil conditions might be vastly different between the test site and the site where the floor covering will actually be used. Floor coverings that test well in one part of the country might perform substantially differently at another site where weather conditions are different or where the local geology results in considerably more or less-abrasive soil conditions. Because of such variability in test conditions, it is difficult to make meaningful comparisons among various types of floor coverings. Similarly, acceptable performance at a particular test site does not guarantee similar performance at a different site.
To avoid the problems associated with using actual pedestrian traffic for test purposes, various types of testing machines have been developed. Such machines typically subject a floor covering sample to repetitive impacts or other physical stresses meant to simulate pedestrian traffic. Because the impact repetition rate can be made much higher and sustained much longer than any floor covering is ever likely to encounter in actual use, testing machines greatly reduce the time needed to run a useful test. Similarly, testing machines make it possible to duplicate test conditions and thereby obtain at least some comparative data from among many test samples. Nevertheless, prior testing machines and test methods were not without deficiencies.
One principal deficiency of prior testing machines and methods was that the impacts applied to the floor covering sample did not accurately simulate actual footfall forces. Thus, although some comparative data could be acquired regarding the performance of samples relative to each other, little absolute information could be acquired regarding how well a particular product would perform in actual use. In other words, a test could tell whether one carpet would last longer than another, but could not tell whether either carpet would last for a specified period of time.
Another deficiency of prior testing machines and methods was that the tests typically took place under artificial conditions. For example, carpet samples were often tested without regard to the sometimes substantial tension actual carpets are placed under when installed. Similarly, the type of subfloor and padding over which the actual carpet would be installed was sometimes ignored in testing. Finally, prior testing did not take into account the type, nature and amount of soil carpets absorb when subjected to actual pedestrian traffic. All these factors affect carpet performance and should be considered if meaningful test data are to be generated.
Still another drawback of prior testing machines and methods was that the machines and methods lacked flexibility. Generally, the machines were configured to perform one type of test only and could not be readily adapted to perform other tests. If additional test information was needed, it was necessary to acquire a completely different machine.